In many technical fields and areas of business, it is of great importance to verify that a given product is genuine. Non-genuine (imitated) products often suffer from poor quality and may damage the reputation of the manufacturer of the genuine product. Also, if the product is of relevance to the safety of a device, the use of an imitated product may lead to damages of a device or accidents.
Bulk liquids are generally more difficult to protect against imitations than solid products, which can be marked by signs, imprints or authentication marks. Small volumes of liquids can be bottled into specific sealed containers, which may then be marked accordingly. These techniques are however not available or not practicable for liquids that are handled in large quantities, such as fuels. Nonetheless, there is also a desire that such liquids be verifiable as genuine product.
This can generally be achieved by adding a specific substance, also referred to as “marker”, in a small quantity. The marker can then be detected by someone wishing to verify the genuineness and authenticity of a product. For instance, it is common practice to add coloring substances, such as dyes, to fuels in order to mark them as genuine brand product.
Yet, the simple color impression obtained by such markers can easily be reproduced by forgers by combining known ingredients, considering that a large number of dyes are commercially available. Further, an identity check that goes beyond a mere visual inspection by the naked eye is difficult to perform on the spot and e.g. at the place of delivery, and usually a time-consuming check of a sample of a delivered liquid in a laboratory needs to be conducted in order to obtain certainty that a delivered liquid is genuine.
There thus is a need for an improved marker that is difficult to forge and that can be easily inspected by a small device e.g. at the place of delivery. Further, such a marker is preferably not visible by inspection with the naked eye, so that a complicated chemical analysis is required to obtain the precise chemical structure of the marker. This represents a further difficulty for counterfeiters, as the necessary equipment such as NMR, HPLC etc. is typically not readily available to counterfeiters. Such a marker is further preferably detectable in minute amounts, so that the marking can be effected efficiently and cheap, while still providing a suitable response that can be detected by small testing devices without the need for highly sophisticated test equipment.
In the medicinal and biological field, semiconducting polymer particles (pdots) have been the subject of research, as they are interesting as nanoprobes due to their non-toxicity, bright photoluminescence, high photostability and fast emission rates. They have mainly been used as in biological applications, such as in biological fluorescence imaging and sensing. The formation of semiconducting polymer particles (pdots), in particular those showing fluorescence and/or phosphorescence, is described in a large number of prior art documents. These include for instance:
“Generation of Functionalized and robust Pdots . . . ”, Yuhui et al, Chem. Commun., 2012, 48, 3161-3163;
“Multicolor conjugated Pdots for biological fluorescence . . . ”, Wu, ACS Nano, 2008, 2 (11), pp 2415-2423; and
“Highly fluorescent pdots for single-molecule . . . ”, Sun et al, SPIE 8812, Biosensing and Nanomedicine VI, 881205 (11 Sep. 2013).
Further information on the preparation and properties of various kinds of pdots can be found in various patents and patent applications, such as US 2012 0282632; US 2013 0266957; WO 2013 116614; US 2008 0146744; US 2013 0234068; and WO 2013 101902, all of which are herewith incorporated by reference.
In the prior art, pdot formation and detection is carried out using bench laboratory equipment, which is big and expensive. Moreover, their operation may require skilled people and the performed analysis can be time-consuming. This limited the application of pdots, and they were thus not considered to represent a possible solution to the problem discussed above with respect to the marking of liquids.
In view of the above, an object of the invention is to provide a solution to the problems formulated above. In particular, it is an object of the present invention to provide a marker for liquids that can easily be identified even when present in only small quantities, and which provides unique identification characteristics that can be analyzed without the need for complicated laboratory equipment, as well as a liquid marked therewith. It is a further object of the invention to provide a liquid protected against counterfeiting by inclusion of a marker, wherein the marker is not visible with the naked eye.
It is a further object of the present invention to provide a cheap and portable solution for the detection of specific markers that can be dissolved in a liquid at low concentration, in particular in fuel liquids, such as refined petroleum products including gasoline, diesel, kerosene, etc. The markers preferably have a good solubility in the liquid, and preferably are difficult to be identified, extracted and separated.
The proposed solutions preferably provide a fast and reliable detection of the presence of a marker inside a liquid, such as liquid fuel.